Excited electronic states from a variational approach based on symmetry-projected Hartree--Fock configurations

Abstract

Recent work from our research group has demonstrated that symmetry-projected Hartree--Fock (HF) methods provide a compact representation of molecular ground state wavefunctions based on a superposition of non-orthogonal Slater determinants. The symmetry-projected ansatz can account for static correlations in a computationally efficient way. Here we present a variational extension of this methodology applicable to excited states of the same symmetry as the ground state. Benchmark calculations on the C${}_2$ dimer with a modest basis set, which allows comparison with full configuration interaction results, indicate that this extension provides a high quality description of the low-lying spectrum for the entire dissociation profile. We apply the same methodology to obtain the full low-lying vertical excitation spectrum of formaldehyde, in good agreement with available theoretical and experimental data, as well as to a challenging model $C_{2v}$ insertion pathway for BeH${}_2$. The variational excited state methodology developed in this work has two remarkable traits: it is fully black-box and will be applicable to fairly large systems thanks to its mean-field computational cost.

References in corpus (2)

• Multi-component symmetry-projected approach for molecular ground state correlations
• Excited electronic states from a variational approach based on symmetry-projected Hartree--Fock configurations

Cited by in corpus (15)

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• Excited electronic states from a variational approach based on symmetry-projected Hartree--Fock configurations
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